Hi 
Better compatibility with the formats sometimes means using a branch early in it's life-cycle and that sometimes means it might not be 100% as stable as the x.x.4 of the earlier branch.
So it's a balancing act for which we each need to find our own comfort-zone.
Usually whichever you choose is good enough to open almost anything. It's increasingly rare to manage to find something that doesn't open at all. It's more a question of how perfect you want it to look. Usually it looks better in LO than just a different version of MSO from whichever one created it but that's not always true either. It's all a bit unpredictable with MSO formats. To some extent that is also true with any format and any program but i tend to find it's mostly MSO formats that suffer most.
The best bet, right now, is to use Doc as an intermediary format. MS have stopped developing new features for it but might still be doing bug-fixes, maybe. So it's less likely to create surprises. DocX keeps popping up with surprises. Odt is stable because it's developed by a committee and LO complies with that although by default it adds a little extra but again that little extra is well documented. So, Odt is likely to become the best choice and i tend to use it like that already because all machines in this office already have LibreOffice. In any other place or for "outsiders" i might use Doc still and i still encourage outsiders to give me Docs (and sometimes that means teaching them where the "Save As..." option is). However, like i said we all need to find our own sweet-spots and see how that changes as ODF becomes more widely accepted.
Regards from
Tom 